This proposal outlines a study to determine whether the decreased levels of AMP aminohydrolase activity observed in muscle tissue of animals or patients with muscular dystrophy are also observed in other tissues from such animals or patients or from patients with other types of inherited disabilities. Following this, we propose to determine whether the decreased levels of enzyme in muscle or other tissues reflects synthesis of an abnormal enzyme, decreased net rate of synthesis and degradation of normal enzyme, lack of synthesis of adult enzyme or loss of enzyme from the cell by diffusion to the extracellular space and eventually the blood stream. The study is to be approached by isolating homogeneous enzyme from different tissues of the same organism, from one tissue of the same organism at different periods of time of development after birth and from the same tissue of normal and abnormal animals. The main progress to date is the successful purification of human erythrocyte AMP aminohydrolase to greater than 90% purity. The enzyme is considerably different from skeletal muscle of rabbits and presumably human skeletal muscle. A new continuous assay involving the determination of ammonia with glutamic dehydrogenase provides a method for determination of activity in crude red blood cell extracts. It will be of interest to determine the level and functional properties of this enzyme from erythrocytes of muscular dystrophic patients.